Monday, May 28, 2012

One Darner of a Day

Yesterday, on May 27, I drove over to the SW corner of Washtenaw County to see what was flying at the Nan Weston Preserve in Sharon Hollow. It's been on my watch list for some time due to the fen that is there along with the shallow streams fed by seeps. A few years ago I found Cordulegaster maculata and C. obliqua on the same day in late May. However, this latest visit was mostly to see if there is any possibility that it could be a site for Tachopteryx thoreyi. I have often wondered if it was possible that there might be small numbers of the Gray Petaltails where we have seeps and and fens in SE Michigan, and Sharon Hollow certainly has some good habitat. After looking around in the area for several seasons, I guess I am now convinced that if it was there, I would definitely have seen one. However, yesterday's trip was made special by the presence of Spatterdock Darners, Rhionaeschna mutata! They were everywhere, and I have never seen so many at one time. Both sexes were flying along the edge of the woods where the powerline right-of-way cuts through the preserve. Some of them were recently emerged, but most of the males were quite mature, with those beautiful sky-blue eyes.
Spatterdock darners are reputed to thrive in fishless ponds, or at least where fish large enough to prey on them are missing. My guess is that some of the many that I was seeing came from the mucky pond that is at the edge of the powerline, and is fed by the fen that's there. Lots of skunk cabbage grows along the margins, but it never dries out. In previous years I have seen a few R. mutata at the site, but never like the numbers that I saw yesterday. I lost count, but it was over several dozen at the margins of the powerline cut. Spatterdock darners typically perch (actually, they hang) from branches or tree trunks while they are maturing, and I think that's when they are most often photographed.

This female is not yet fully mature, as can be seen by the dark eyes and muted colors. I have also seen R. mutata take cover on trees on shrubs when it has started to rain, as well as a sort of siesta when it has been hot and sunny. Mostly though, one sees them "perch" when they are still maturing. The wings have a slight amber tinge at that stage as well.

After I was finished at the Nan Weston Preserve, I decided to continue down Easudes Road into Jackson County and collected in the Sharonville State Wildlife Management Area (you can always tell when you are in a State Game Area, because so many morons think signs are wildlife). As I crossed one four-corners, I saw dozens more R. mutata flying in the roadway in what appeared to be feeding swarms. In one opening at the edge of a field I saw dozens more feeding, and some were perched on shrubs. One perched male looked like he had emerged within a few hours. As I drove along towards Tamarack Lake, I saw more darners flying along the road. I parked at the Tamarack Lake site, and took the trail down to the lake. In the field edges, I saw more R. mutata. This has to have been an epic emergence of Spatterdock darners. I also saw a bunch of Libellula cyanea at Tamarack Lake -- a very pretty skimmer with black and white stigmas. Spangled skimmers are not everywhere, but mucky-bottomed lakes with shallow margins seem to be a good place to look.

After I got home from my trip, I spent some time in the front yard, and what did I see? An immature Spatterdock Darner on the tree in front of the house! I watcher her for some time, and I wonder where she emerged from. All told, I would estimate that I saw close to a hundred darners yesterday, so there would have been may thousands out there that I did not see, which really boggles my mind. It truly was a darner day.

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